Preparation of Mo6+, Gd3+-doped TiO2 nanotube arrays and study of their organization and photocatalytic properties

Titanium dioxide nanotube arrays doped with Mo[Formula: see text], Gd[Formula: see text], and Mo[Formula: see text]-Gd[Formula: see text] were prepared by anodic oxidation combined with a two-step electrochemical method. The crystalline structure, surface morphology, light absorption properties, and crystalline transformation process were characterized using XRD, SEM, UV–Vis, DSC, and FT-IR. The results show that Mo[Formula: see text] and Gd[Formula: see text] single doping of TiO 2 can promote the transformation of amorphous TiO 2 to anatase and inhibit the transformation of anatase phase to rutile, but Mo[Formula: see text]–Gd[Formula: see text] co-doping promotes both phase transformations, and the anatase compositions of the TiO 2 heat-treated at 450[Formula: see text]C were all over 91%; The tube diameters of TiO 2 nanotubes were all around 60–70 nm; the Mo[Formula: see text]- and Gd[Formula: see text]-doped TiO 2 light absorption peaks were all significantly red-shifted, with the most obvious change in the Mo[Formula: see text]–Gd[Formula: see text]co-doping, where the forbidden bandwidth was reduced to 3.01 eV; The degradation rate of pure TiO 2 photocatalytic degradation of methylene blue for 8 h was only 41.9%, while the degradation rate of Mo[Formula: see text]–Gd[Formula: see text] co-doped TiO 2 was as high as 91.51%; Mo[Formula: see text], Gd[Formula: see text], single doping and co-doping could increase the amount of [Formula: see text] OH, [Formula: see text] OOH adsorbed on the surface of TiO 2 , which led to the improvement of catalytic performance.